For three seasons with Mike Zimmer at the helm, the formidable Minnesota Vikings defense had been lumped in with the league’s best. But one particular shortcoming kept it from realizing its full potential: A rush defense that had yet to catch up to the team’s outstanding work against the pass.

Bolstered by Zimmer’s expertise with defensive backs, Minnesota’s pass defense finished seventh, 12th and third in the coach’s previous three seasons, but that was offset by a rush defense that came in 25th, 17th and 20th. In 48 regular-season games since Zimmer took over, the Vikings had allowed 112.5 yards per game on the ground.

This season, the script has flipped. Minnesota currently ranks third in yards per game against the run at 78.7. They have only allowed two teams to rush for over 100 yards: the Chicago Bears (115) and Pittsburgh Steelers (102), who are both in the league’s top-10.

In addition to having massive nose tackle Linval Joseph clogging the middle and a pair of strong, speedy linebackers playing in the nickel defense, the Vikings’ greatest catalyst in run stopping might be its secondary.

According to Pro Football Focus, Trae Waynes has the best run-stop percentage of any corner in the league, Harrison Smith is one of seven safeties not to miss a tackle against the run, and Xavier Rhodes is one of six corners who hasn’t missed a tackle against either the run or pass this season.

“Trae’s tackled well, Harrison tackles well, Xavier, [Andrew] Sendejo, those guys all tackle pretty well,” said Zimmer. “Honestly, whether you’re good or bad in the run game, the perimeter run force is big because your big plays come out of that, so your average ends up going up if you give up a lot of big plays in the running game.”

The 3.2 yards per carry allowed by the Vikings is third in the NFL, behind only Denver and Cleveland. As Zimmer alluded, the Vikings have excelled at reducing big plays.

SportingCharts.com has been tracking “big plays” since 2009, which they define as a 25-yard pass or a 10-yard run. The lowest number of 10-yard running plays a team has allowed since 2009 is 22, which Pittsburgh accomplished in 2010.

The Vikings have currently allowed just six, which puts them on pace for 16. Against the Saints, Buccaneers and Packers, Minnesota didn’t allow a single carry of 10 yards or more. They allowed an 11-yard run to Pittsburgh’s Le’veon Bell, runs of 11 and 13 yards to Chicago’s Jordan Howard, a 13-yard scramble to Chicago’s Mitchell Trubisky and runs of 12 and 29 yards to Detroit’s Ameer Abdullah, who gave the Vikings as much trouble as any back this season.

“I know everybody talked about two weeks ago when we played Detroit,” Zimmer said on Sunday. “Tackling some of these running backs in space is like catching a chicken in a big yard.”

The Vikings benefit from having a good combination of speed, size and strength at the corner positions. Both Rhodes and Waynes possess superb quickness to stick with ball-carriers, the length to wrap them up and the power to get them to the ground.

“You don’t always see defenses with corners that are willing to throw it up in there like our guys do, who can cover and they can tackle,” said Sendejo. “That’s part of your job. You have to be able to do both depending on the call and what we’ve got going on that week defensively.”

Having held five of the first six opponents to under 20 points, the Vikings defense looks as cohesive as ever under Zimmer, and the blossoming run defense might be why.

“A lot of what we do around here is just preaching that you do your job to allow someone else to do their job, and we all buy in,” said Sendejo, “and that’s what we do.”

Sam Ekstrom is a Zone Coverage staff writer and hosts Locked On Vikings for the Locked On Podcast Network with former NFL QB Sage Rosenfels. He is a high school play-by-play voice, primarily at BCTV and Prep Spotlight, and a former sports radio host at 105 The Ticket. Follow Sam on Twitter @SamEkstrom.